UPSC is a 3 stage   selection process involving Prelims, Mains and Interview which tests your personality test. Prelims has 2 Papers namely General Studies and CSAT.

General Studies has Current Events, History of India and Indian National Movement, Indian and World Geography, Indian Polity and Governance, Economic and Social Development, Environmental Ecology, Biodiversity and Climate Change and General Science.

CSAT has Comprehension, Interpersonal skills including communication skills, Logical Reasoning and Analytical ability, Decision making and problem solving, General Mental Ability, Basic numeracy and Data Interpretation.

If you look at this, you need strategic preparation. If you can atleast start preparing ahead of 1- 2 years it willl be ideal. If you are preparing at home, you need to keep yourself away from distractions and focus on the goal ahead. Gather as much as information as you can on each topic and keep yourself updated. Practise mock test papers.

Few books that you can refer are:

Indian Polity for Civil Services bby M. Laxmikanth

Indian Art and Culture by Nitin Singhania

Certificate Physical and Human Geography by Gog Cheng Leong

Oxford School Atlas by Oxford Publishers

Indian Economy by Ramesh Singh

Economic Survey by Ministry of Finance

India Year Book

A Brief History of Modern India by Rajiv Ahir

Hi,
It's really not necessary to take coaching classes for UPSC. You can easily prepare yourself for it. Start by studying from NCERT books and then move to other authors book. You can also refer to YouTube for better understanding. Also make notes for future reference.